Here is the part of the Program Terms and Conditions that addresses this topic:
1.4 Conditions of Enrollment
1.4.b. Individual Membership. Only individuals are eligible for Loyalty Program membership, and each individual may maintain only one Membership Account. All Loyalty Member Accounts are individual Accounts and no joint Accounts are permitted. Loyalty Program benefits are non-transferable unless expressly stated otherwise.
Source:
https://www.marriott.com/loyalty/terms/default.mi
If Marriot (or someone at a hotel decides to report you to Marriott) discovers that you are sharing you account, the following may happen:
1.7 Other Conditions of Enrollment
1.7.a. Cancelling or Suspending Membership Accounts
ii. Cancelling or Suspending by the Company. The Company may cancel a Member’s accumulated Points, suspend Loyalty Program benefits, suspend Elite Membership Status, suspend Lifetime Elite Membership Status (which will subsequently also remove protection against the forfeiture of Points should the member become inactive as described in Section 1.5.d. or cancel a Member’s Account at any time with immediate effect and without written notice, for any reason and in the Company's sole discretion including, without limitation, if the Company believes the Member has:
D. Breached or violated any of these Program Rules or the Website Terms of Use;
Source: Same as above
I strongly suggest you follow the advice given and stop sharing your account. All it takes is one zealous person having a bad day and you will lose all of your points. And as
SPN Lifer noted, you can transfer points. It's actually a part of the Program Terms and Conditions:
2.8 Transferring Points from One Account to Another
2.8.a. In accordance with the conditions for transferring Points as described in Section 1.6.c., a Member can transfer up to a maximum of 100,000 Points per calendar year to another Membership Account as long as both Accounts are in good standing and have each been open for at least thirty (30) days with qualifying activity, ninety (90) days without qualifying activity (see 2.8.b). A Member can receive up to a maximum of 500,000 Points per calendar year from other Membership Accounts as long as the Accounts are in good standing and have each been open for at least thirty (30) days with qualifying activity, ninety (90) days without qualifying activity.
Source: Same as above